Flip-up helmet



FIG. 1 is a perspective view of a flip-up helmet according the new design;

FIG. 2 is a right side elevational view of the flip-up helmet of FIG. 1;

FIG. 3 is a left side elevational view of the flip-up helmet of FIG. 1;

FIG. 4 is a front elevational view of the flip-up helmet of FIG. 1;

FIG. 5 is a rear elevational view of the flip-up helmet of FIG. 1;

FIG. 6 is a top plan view of the flip-up helmet of FIG. 1; and,

FIG. 7 is a bottom plan view of the flip-up helmet of FIG. 1. 

The ornamental design for a flip-up helmet, as shown and described. 